Time is money to mechanics and it is important for them to be able to diagnose a problem as soon as possible. There are in general two kinds of fuel systems for internal combustion motors. These motors use fuel injectors or carburetors. Both of these systems require fuel pumps and electrical control systems connected to the fuel pumps for their operation. If an internal combustion motor is not operating properly, or at all, it is important to be able to diagnose the problem as soon as possible. Depending on the fuel supply system for the motor, the problem could be in the fuel injectors or the carburetor, or the fuel pumps, or the electrical control systems which are connected to the fuel pumps. To determine this the fuel injectors or carburetors, depending on the motor, have to be examined to determine if they are defective or not. If they are not defective, the attention of the mechanic will be directed to the fuel pumps and their attached electrical control systems.